1. Field of the Invention
The present invention relates to a pigment particle having a yellow hue, and an ink, an ink cartridge, and an ink jet recording method each using the pigment particle.
2. Description of the Related Art
In recent years, there has been a growing demand for an improvement in lightfastness of an image recorded by an ink jet recording method. To cope with such demand, an investigation has been vigorously conducted on an ink using a pigment as a coloring material. However, an image recorded with the ink using the pigment as a coloring material has lower color developability than that of an image recorded with an ink using a dye as a coloring material. Particularly in the case of an image recorded with a yellow ink, it has been a subject to achieve both its lightfastness and color developability.
In addition, an ideal color tone of a yellow coloring material is such that its hue angle in a CIE L*a*b* colorimetric system is 90°. In actuality, however, a deviation of the color tone toward greenish yellow (whose hue angle is larger than 90°), reddish yellow (whose hue angle is smaller than 90°), or the like occurs owing to, for example, a light absorption characteristic of a pigment. In the case of a yellow coloring material to be used in ink jet recording, the greenish yellow is apt to be recognized as a dull color by the human eye and hence provides such an impression that image vividness is low. Accordingly, the reddish yellow is more suitable than the greenish yellow from the viewpoint of color developability.
Further, in the ink jet recording, plain paper or a recording medium having a coating layer (e.g., glossy paper or art paper) has also become used as a recording medium. Accordingly, it has been such a demanded that an ink to be used in the ink jet recording be capable of realizing high color developability in any one of those various recording media. A method involving using one or more kinds of pigments among C.I. Pigment Yellows 213, 185, and 155 as coloring materials has been proposed for achieving both lightfastness and color developability (see Japanese Patent Application Laid-Open No. 2008-266568).
In addition, there has been a proposal concerning a method involving performing a treatment with a microreactor to produce fine particles of a pigment (International Application No. WO2009/008338). International Application No. WO2009/008338 discloses that such treatment with the microreactor can change the crystal form of the pigment, and describes that α- and γ-type quinacridone pigments were produced. Meanwhile, International Application No. WO2010/035861 disclose that when a copper phthalocyanine pigment is subjected to the similar treatment as disclosed in International Application No. WO2009/008338, its absorption characteristics in a visible light region become different from conventional ones, though its crystal form does not change.